Double-acting piston

Abstract

The double-acting piston ( 1 ) includes a lower half-piston ( 13 ) and an upper half-piston ( 14 ), the periphery of each the half-piston ( 13, 14 ) coming into radial stop with a radial traction disc ( 30 ) which is tightly held by a clamping screw ( 29 ) between the two half-pistons ( 13, 14 ) on the one hand, in its center, between a lower central clamping surface ( 19 ) and an upper central clamping surface ( 20 ) and, on the other hand, at its periphery, between a lower peripheral clamping surface ( 21 ) and an upper peripheral clamping surface ( 22 ), the clamping by the screw ( 29 ) of the disc ( 30 ) resulting in prestressing the lower piston cap ( 15 ) and the upper piston cap ( 16 ) that the lower half-piston ( 13 ) and the upper half-piston ( 14 ) respectively have.

1 . A double-acting piston ( 1 ) operable at high temperature and cooperating with transmission means ( 8 ) to move in a cylinder ( 2 ) whose end which opens on the side of said means ( 8 ) is closed by a lower cylinder head ( 4 ) to define with said piston ( 1 ) a lower hot gas chamber ( 6 ), and whose other end is closed by an upper cylinder head ( 5 ) to define with said piston ( 1 ) an upper hot gas chamber( 7 ), the transmission means ( 8 ) being accommodated in a transmission case ( 3 ) on which is fixed, directly or indirectly, the cylinder ( 2 ) characterized in that it comprises:
 A lower half-piston ( 13 ) having a lower piston cap ( 15 ) facing the lower hot gas chamber ( 6 ), said cap ( 15 ) being prolonged by a lower piston rod ( 17 ) which passes through the lower cylinder head ( 4 ) via a lower rod orifice ( 37 ) provided in said cylinder head ( 4 ), said rod ( 17 ) being directly or indirectly integral with transmission means ( 8 ), while the face of said half-piston ( 13 ) opposite to said cap ( 15 ) is hollow and constitutes a lower relief recess ( 25 );   A lower central pillar ( 23 ), coaxial with the lower half-piston ( 13 ) which is accommodated in the lower relief recess ( 25 ) to terminate by a lower central clamping surface ( 19 );   At least one lower peripheral clamping surface ( 21 ) provided at the lower half-piston ( 13 ) and bordering the lower relief recess ( 25 ) at the periphery of said half-piston ( 13 );   At least one lower radial limit stop ( 35 ) provided in the lower half-piston ( 13 ) near the lower peripheral clamping surface ( 21 );   A lower clamping screw bore ( 27 ) provided in the lower half-piston ( 13 ) at its center, and which passes through said half-piston ( 13 ) from one side to the other in an axial direction;   An upper half-piston ( 14 ) having a upper piston cap ( 16 ) oriented opposite to the upper hot gas chamber ( 7 ), said cap ( 16 ) being prolonged or not by an upper piston rod ( 18 ) that penetrates or passes through the upper cylinder head ( 5 ) via an upper rod orifice ( 38 ) provided in said cylinder head ( 5 ), while the face of said half-piston ( 14 ) opposite to said cap ( 16 ) is hollow and constitutes an upper relief recess ( 26 );   An upper central pillar ( 24 ), coaxial with the upper half-piston ( 14 ), which is accommodated in the upper relief recess ( 26 ) to end in an upper central clamping surface ( 20 );   At least one upper peripheral clamping surface ( 22 ) arranged on the upper half-piston ( 14 ) and bordering the upper relief recess ( 26 ) at the periphery of said half-piston ( 14 );   At least one upper radial limit stop ( 36 ) provided in the upper half-piston ( 14 ) near the upper peripheral clamping surface ( 22 );   An upper clamping screw bore ( 28 ) provided in the top half-piston ( 14 ) at its center, and which passes through said half-piston ( 14 ) from one side to the other in an axial direction;   At least one radial traction disc ( 30 ), perforated or not, pierced at its center with a screw passage orifice ( 31 ) whose outer diameter is close to that of the double-acting piston ( 1 ), whose central zone ( 32 ) is tightly mounted between the lower central clamping surface ( 19 ) and the upper central clamping surface ( 20 ), whose peripheral zone ( 33 ) is tightly mounted between the lower peripheral clamping surface ( 21 ) and the upper peripheral clamping surface ( 22 ) and whose periphery comprises at least one radial traction stop ( 34 ) which can cooperate with the lower radial limit stop ( 35 ) and/or the upper radial limit stop ( 36 );   A clamping screw ( 29 ) housed partly in the lower clamping screw bore ( 27 ) and partly in the upper clamping screw bore ( 28 ), the first end of said screw ( 29 ) being made integral with transmission means ( 8 ) while the second end of said screw ( 29 ) is made integral with the upper piston rod ( 18 ) or the upper piston cap ( 16 ).   
     
     
         2 . The double-acting piston according to  claim 1 , characterized in that the thickness and the geometry of the radial traction disc ( 30 ) as well as the axial position of the lower central clamping surface ( 19 ), of the upper central clamping surface ( 20 ), of the lower peripheral clamping surface ( 21 ) and of the upper peripheral clamping surface ( 22 ) are provided so that when the clamping screw ( 29 ) is tightened while mounting the double-acting piston ( 1 ), said disc ( 30 ) is first compressed between the lower peripheral clamping surface ( 21 ) and the upper peripheral clamping surface ( 22 ) before being compressed between the lower central clamping surface ( 19 ) and the upper central clamping surface ( 20 ). 
     
     
         3 . The double-acting piston according to  claim 2 , characterized in that the radial position of the radial traction stop ( 34 ) relative to that of the lower radial limit stop ( 35 ) and/or that of the upper radial limit stop ( 36 ) is provided so that when the clamping screw ( 29 ) is tightened while mounting the double-acting piston ( 1 ), said lower ( 35 ) and/or upper ( 36 ) radial limit stop comes in contact with the radial traction stop ( 34 ) and limits the diameter of the lower half-piston ( 13 ) and/or the upper half-piston ( 14 ). 
     
     
         4 . The double-acting piston according to  claim 1 , characterized in that the radial traction disc ( 30 ) has at its periphery a ring groove ( 39 ) which can accommodate sealing means ( 40 ). 
     
     
         5 . The double-acting piston according to  claim 4 , characterized in that the ring groove ( 39 ) is housed in a groove of groove ( 42 ) that is commonly constituted by a lower overhang ( 43 ) comprised by the lower half-piston lower ( 13 ) in its periphery, and an upper overhang ( 44 ) comprised by the upper half-piston ( 14 ) in its periphery. 
     
     
         6 . The double-acting piston according to  claim 1 , characterized in that at least one air supply radial duct ( 45 ) is arranged in the thickness of the radial traction disc ( 30 ), said duct ( 45 ) connecting the screw through-hole ( 31 ) to the periphery of said disk ( 30 ). 
     
     
         7 . The double-acting piston according to  claim 6 , characterized in that the radial traction disc ( 30 ) consists of two radial traction half-discs ( 46 ) on the surface of at least one of which is arranged at least one radial duct groove ( 47 ) which constitutes the air supply radial duct ( 45 ) when said two half-discs ( 46 ) are pressed against one another as a result to the clamping of the clamping screw ( 29 ). 
     
     
         8 . The double-acting piston according to  claim 1 , characterized in that the end of the upper piston rod ( 18 ) which is furthest from the piston upper cap ( 16 ) is always immersed in a pressure chamber ( 49 ) filled with compressed air ( 54 ) whatever the position of the double-acting piston ( 1 ) in the cylinder ( 2 ), said chamber ( 49 ) being integral or not with the upper cylinder head ( 5 ) and being connected to a pressurized air source ( 50 ) from which compressed air ( 54 ) originates, while said end has at least one air supply channel ( 48 ) connecting the upper clamping screw bore ( 28 ) with the pressure chamber ( 49 ). 
     
     
         9 . The double-acting piston according to  claim 8 , characterized in that the air supply channel ( 48 ) consists of a radial groove arranged either on the flat end of the upper piston rod ( 18 ) which is furthest from the upper piston cap ( 16 ) or on at least one side of a screw thrust washer on which the clamping screw ( 29 ) rests. 
     
     
         10 . The double-acting piston according to  claim 8 , characterized in that a screw cooling tube ( 53 ) surrounds the clamping screw ( 29 ) on all or part of its length, compressed air ( 54 ) coming from the pressurized air source ( 50 ) being able to circulate in a space left between the inner wall of said tube ( 53 ) and the outer surface of the clamping screw ( 29 ) while the greatest possible part of the outer surface of said tube ( 23 ) does not touch the internal wall of the upper clamping screw bore ( 28 ) so as to define a vacuum space with the latter wall. 
     
     
         11 . The double-acting piston according to  claim 10 , characterized in that the screw cooling tube ( 53 ) comprises a tube flange ( 55 ) held tightly by the clamping screw ( 29 ) against the end of the upper rod piston ( 18 ). 
     
     
         12 . The double-acting piston according to  claim 10 , characterized in that the screw cooling tube ( 53 ) comprises at least a tube bulge ( 56 ) consisting of an axial portion of said tube ( 53 ) whose diameter is substantially equivalent or even slightly greater than that of the upper clamping screw bore ( 28 ) or the lower clamping screw bore ( 27 ) in which it is housed. 
     
     
         13 . The double-acting piston according to  claim 10 , characterized in that the screw cooling tube ( 53 ) comprises at least one tube diameter restriction ( 57 ) consisting of an axial portion of said tube ( 53 ) whose diameter is substantially equivalent or even slightly lower than that of the body of the clamping screw ( 29 ). 
     
     
         14 . The double-acting piston according to  claim 10 , characterized in that the screw cooling tube ( 53 ) has at least one radial communication hole ( 58 ) which allows the compressed air ( 54 ) to enter into said tube ( 53 ), or to escape from it. 
     
     
         15 . The double-acting piston according to  claim 1 , characterized in that the lower rod orifice ( 37 ) and/or the upper rod orifice ( 38 ) cooperates with—or comprises—rod sealing means ( 59 ) creating a seal between the lower piston rod ( 17 ) and the lower cylinder head ( 4 ) and/or between the upper piston rod ( 18 ) and the upper cylinder head ( 5 ). 
     
     
         16 . The double-acting piston according to  claim 15 , characterized in that the rod sealing means ( 59 ) comprise an upper rod seal ( 60 ) and a lower rod seal ( 61 ) sufficiently distant from one another to form—between said two seals ( 60 ,  61 )—an oil flow chamber ( 62 ) into which a cooling-lubricating oil supply duct ( 63 ) enters, and out of which a cooling-lubricating oil outlet duct ( 64 ) goes. 
     
     
         17 . The double-acting piston according to  claim 16 , characterized in that the rod sealing means ( 59 ) cooperate with a rod guiding ring ( 66 ) housed inside or outside the oil flow chamber ( 62 ).